Can knee flexion contracture affect cervical alignment and neck tension? A prospective self-controlled pilot study

Area of Science:

• Orthopedics and Biomechanics
• Spinal and Extremity Alignment
• Musculoskeletal Health

Background:

• Proper alignment of lower extremities and cervical spine is crucial for balance and maintaining horizontal gaze.
• Malalignment in one body segment can lead to compensatory changes in other areas, affecting global posture.
• Knee flexion contracture (KFC) is associated with spinal inclination and potential disruption of cervical alignment and neck tension (NT).

Purpose of the Study:

• To investigate the impact of knee flexion contracture (KFC) on cervical spine alignment.
• To assess the potential effects of KFC on posterior muscle function and neck tension (NT).

Main Methods:

• A prospective pilot study involving 22 patients with KFC and 12 controls, comparing pre-operative and post-operative phases.
• Radiographic measurements of sagittal alignment (e.g., C7 SVA, T1 slope, lumbar lordosis) and cervical range of motion (ROM).
• Assessment of posterior muscle function using electromyography (flexion-relaxation ratio, FRR) and ultrasound elastography (SWE), alongside patient-reported outcomes (VAS, NDI).

Main Results:

• Pre-operatively, KFC patients exhibited poorer spinal alignment (e.g., increased C7 SVA) and reduced ROM compared to controls.
• Post-operative correction of KFC significantly improved spinal alignment, reduced neck tension (VAS, NDI), and increased ROM.
• Knee flexion angle strongly correlated with lumbar lordosis, C7 SVA, and cervical alignment parameters, which in turn correlated with neck muscle function and patient-reported outcomes.

Conclusions:

• Knee flexion contracture can induce spinal inclination and craniocervical malalignment, contributing to neck tension and reduced range of motion.
• Surgical correction of KFC shows potential to alleviate these associated spinal and cervical issues.
• This pilot study highlights the interconnectedness of lower extremity and cervical spine alignment, suggesting implications for clinical management and future research.